Tanning process



Patented Dec. 5, 1933 UNITED STATES PATENT OFFICE W. Witzel, Ingram, Pa.,

assignors to The Selden Company, Pittsburgh, Pa., a corporation} of Delaware No Drawing. Application March 5, 1981 Serial No. 520,456

12 Claims.

This invention relates to the taming of hides, skins and the like, using a new class of taming materials.

According to the invention, leather is produced by the tanning of hides and skins in the presence of a new class of tanning agents, which may be used alone or in admixture with other vegetable or artificial tanning materials. The new tanning agents of the present invention are compounds of the group consisting of (1) the condensation products obtained by reacting carbohydrates, and aromatic hydrocarbons, with sulfuric acid or aldehydes and (2) the alkali metal salts produced by the neutralization of these products with alkali metal bases, it being understood that the reaction products of both crude and purified materials may be used. These substances are new chemical products but are not claimed as such in the present application, this forming the subject matter of my co-pending application Serial No. 518,291 filed February 25,

1931. Residues of aromatic compounds suitable for use in the practice of the invention are described in the following patents and applications:

Jaeger and Daniels applications Serial No, 438,234 filed March 22, 1930; Serial No. 367,738 filed Oct. 5, 1929; Serial No. 397,733 filed Oct. 5,

1929; Serial No. 404,202 filed Nov. 1, 1929; Patent No. 1,693,713; Patent No. 1,764,031; Patent No. 1,831,059.

As is brought out in the application just referred to, these tanning materials can be readily prepared from very cheap materials, and are characterized by a good light color and excellent tanning properties. They possess rapid penetrating qualities as compared with the vegetable tans and are thus not only valuable tanning agents when used alone but are also well suited for mixture and use with the ordinary vegetable tans,

40 such as oak bark extract, chestnut, hemlock,

gambier, quebracho, sumac, etc.

Condensation products defined under (1) above contain free sulphonic acid groups and are therefore quite strongly acid in reaction, whereas the alkali metal salts are ordinarily neutral or alkaline and acetic acid, phosphoric acid, lactic acid, etc., may be added to correct the pH value. The use of these tanning materials takes place in dilute or moderately concentrated aqueous solutions, but the new tanning materials, and particularly those containing alkali metal salts, can be admixed with vegetable tanning extracts during concentration or shipment as they exert a favorable stabilizing action against oxidation and precipitation of the tanning content. When used for the tanning of hides either alone or in conjunction with vegetable tanning materials, they exert a rapid tanning action and produce a strong, light colored leather having good mechanical strength.

While the condensation products of the present invention are of general value in conjunction with all vegetable tanning extracts, they are of especial value when used with the more astringent tans such as quebracho, hemlock and the like. In the process of vegetable tanning it is well known that the rate of difiusion, and consequently the rate of tannage is inversely proportional to the astringency of the tan used. Such extracts as those of quebracho, hemlock, larch, etc. therefore require considerably longer time to completely tan the hides than do the less astringent tans such as gambier, probably because the more astringent tans immediately effect such a complete tannage at the surface that rapid penetration is retarded. The addition of the tanning materials of the present invention to the liquors of an astringent vat aids in penetration, not only by acting as a less astringent diluent, but also by the fact that its more rapid penetration effects a partial tannage in advance of the vegetable extract, thus preventing imperviousness of the outer portions of the hide. The invention is not limited however to the use of the novel tanning agents in conjunction with more astringent tans but on the contrary their properties are such that they may be used alone or in conjunction with any material having tanning or non-tanning properties.

The invention will be further illustrated in conjunction with the following examples to which, however, the invention is not limited. The parts are by weight.

Example 1 50 parts of cellulosein the form of old sulfite paper are introduced into 750 parts of concentrated sulfuric acid, thorough agitation and cooling being provided. Thereupon 134 parts of the residue from the furfural purification of anthracene containing phenanthrene, carbazole, dead oils, etc. are stirred in and the stirring continued until all of the residue dissolves. As is stated on page 1 of my prior Patent No. 1,693,713 these residues normally contain considerable amounts of furfural, which enters into the condensation reaction. The product so obtained, consisting of a reaction product of cellulose, aromatic hydrocarbons, sulfuric acid and furiural, is a part of the present invention. The

mass is then poured into 10,000 parts of water, the excess acid neutralized with lime, filtered, and the calcium salt transformed into the sodium salt by means of sodium carbonate. On evaporating the filtered solution, a brownish mass is obtained which is the sodium salt of the condensation product. The yield amounts to 175% by weight of the cellulose and anthracene residue.

50 parts of the intermediate condensation product are then treated with 250 parts of 40% sulfuric acid and 10 parts of 30% formaldehyde solution, the mixture being stirred vigorously and heated to 80 C. for about half an hour, the stirring then being continued as the material gradually cools down. The odor of aldehyde should disappear in about two hours. A black mass is obtained which is readily soluble in water and which is an excellent tanning agent. The black mass is stirred into 700 parts of cold water and milk of lime containing 200 parts of CaO is added, neutralization being completed with calcium carbonate. After filtering, the liquid may be evaporated to produce a solid product, or, preferably, the calcium is exchanged for sodium by treatment with soda ash, followed by a second filtration. The sodium salt is readily soluble in water and is an excellent tanning agent.

The formaldehyde may be substituted by acetaldehyde, or a mixture of acetaldehyde and formaldehyde may be used.

The hides, delimed and bated, are introduced into a tanning bath containing 40 grams per liter of the above described condensation product together with suitable amounts of oak bark tanning extract, being allowed to remain with suitable agitation after the tanning action is well started, until complete tannage is effected. The leather obtained after washing and the usual further treatments, is of good appearance and of excellent strength.

Example 2 50 parts of cellulose in the form of old sulfite paper are introduced into 750 parts of concentrated sulfuric acid, thorough agitation and cooling being provided. Thereupon 134 parts of the residue from the sublimation of crude naphthalene in the catalytic phthalic anhydride process are stirred in and the stirring continued until all of the residue dissolves. The mass is then poured into 10,000 parts of water, the ex cess acid neutralized with lime, filtered, and the calcium salt transformed into the sodium salt by means of sodium carbonate. On evaporating the filtered solution, a light brown mass is obtained which is the sodium salt of the condensation product. The yield amounts to ISO-170% by weight of the cellulose and naphthalene residue.

This intermediate condensation product is treated with aldehyde and sulphuric acid in the same manner as described in Example 1. A soft brownish mass is obtained which is soluble in water and can be used directly as a tanning agent or transformed into its alkali metal salt.

Hides, suitably delimed and bated, are tanned in a bath of the above described condensation product or of its alkali metal salt, the solution in the latter case being brought to a suitable pH value of 1-5 by the addition of acetic acid. The strength of the original solution may vary from 20-35 grams per liter, the concentration being increased as the tannage nears completion.

Example 3 I 50 parts of cellulose in the form of old sulfite paper are introduced into 750 parts of concentrated sulfuric acid, thorough agitation and cooling being provided. Thereupon 134 parts of the residue from the vaporization of crude anthracene in the catalytic anthraquinone process are stirred in and the stirring continued until all of the residue dissolves. The mass is then poured into 10,000 parts of water, the excess acid neutralized with lime, filtered, and the calcium salt transformed into the sodium salt by means of sodium carbonate. On evaporating the filtered solution, a dark brown mass is obtained which is the sodium salt of the condensation product. The yield amounts to 173% by weight of the cellulose and anthracene residue.

The intermediate condensation product is treated with aldehyde and sulfuric acid in the same manner as described in Example 1. A soft brownish soluble mass is obtained which in the form of its alkali metal salt is an excellent tanning agent and can be used alone or in admixture with other tanning material.

A bath is prepared of equal parts of the foregoing condensation product and oak bark extract, and is acidified to a pH value of 1-5 and is used for the tanning of heavy ox hides such as those used in preparing a sole leather. A much shorter period of tannage is required than when the vegetable tan is used alone. and a full leather having excellent strength and wearing qualities is obtained.

Example 4 1500 parts of 100% sulfuric acid are cooled to 20 C. and parts pure phthalic anhydride are slowly added. After addition is complete, 100 parts cellulose in the form of waste paper or the like are added with stirring during two hours, and the mixture is further stirred with cooling for a period of three to six hours.

In the preparation of the above composition the phthalic anhydride is chemically condensed with the sulfuric acid and cellulose. In the final product itacts as an improved loading agent, having no injurious effect on the solubility in water of the mass, but serving to increase the weight and fullness of the leather. 4

After the reaction is complete, 268 parts of a residue from the vaporization of semi-purified anthracene with air in the catalytic oxidation of anthracene to anthraquinone are added with constant stirring, the temperature being maintained below 25 C. and the stirring is continued until the reaction is completed.

The intermediate condensation product is treated with aldehyde and sulfuric acid in the same manner as described in Example 1. A soft brownish soluble mass is obtained which in the form of its alkali metal salt is an excellent tanning agent and can be used alone or in admixture with other tanning material as in previous examples.

What is claimed as new is:

1. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one compound included within the group consisting of condensation products obtained by reacting carbohydrates, and aromatic hydrocarbons, with sulfuric acid and aldehydes, and the alkali metal salts of the condensation product.

2. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one compound included within the group consisting of condensation products obtained by reacting carbohydrates, and aromatic hydrocarbons, with sulfuric acid and aldehydes, and the alkali metal salts of the condensation product, the solution being slightly acid.

3. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one compound included within the group consisting of condensation products obtained by reacting carbohydrates, and aromatic hydrocarbons, with sulfuric acid and formaldehyde, and the alkali metal salts of the condensation product.

4. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one compound included in the group consisting of condensation products obtained by the simultaneous reaction of carbohydrates, aromatic hydrocarbons, sulfuric acid and furfural, and the alkali metal salts of the condensation product.

5. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one compound included within the group consisting of condensation products obtained by reacting a carbohydrate, and a residue from the purification of crude anthracene, with sulfuric acid and an aldehyde, and the alkali metal salts of the condensation product.

6. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one compound included within the group consisting of condensation products obtained by reacting cellulose, and a residue from the purification of crude anthracene, with sulfuric acid and an aldehyde, and the alkali metal salts of the condensation product. Y

7. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one condensation product obtained by reacting a carbohydrate, and a substance included in the group consisting of residues from solvent purification of crude anthracene with phenanthrene and carbazol solvents, residues from solvent purification of crude anthracene with phenanthrene solvents, residues from the vaporization of impure anthracene, residues from the vaporization of crude naphthalene, with sulfuric acid and an aldehyde.

8. A process of tanning hides, which comprises treating them with an aqueous solution containing at least one alkali metal salt of a condensation product obtained by reacting a carbohydrate, and a substance included in the group consisting of residues from solvent purification of crude anthracene with phenanthrene and carbazol solvents, residues from solvent purification of crude anthracene with phenanthrene solvents, residues from the vaporization of impure anthracene, residues from the vaporization of crude naphthalene, with sulfuric acid and an aldehyde.

9. A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one condensation product obtained by reacting a carbohydrate, and a phthalic anhydride substance, an aromatic hydrocarbon, sulfuric acid and an aldehyde.

10. A process of tanning hides, which comprises treating the hides with an aqueous solutioncontaining at least one condensation product obtained by reacting a carbohydrate, and a phthalic anhydride substance, an aromatic hydrocarbon, sulfuric acid and formaldehyde.

11. A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one condensation product obtained by reacting a carbohydrate, a phthalic anhydride substance, and a substance included in the group consisting of residues from solvent purification of crude anthracene with phenanthrene and carbazol solvents, residues from solvent purification of crude anthracene with phenanthrene solvents, residues from the vaporization of impure anthracene, residues from the vaporization of crude naphthalene, with sulfuric acid and an aldehyde.

12. A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one alkali metal salt of a condensation product obtained by reacting a carbohydrate, a phthalic anhydride substance, and a substance included in the group consisting of residues from solvent purification of crude anthracene with phenanthrene and carbazol solvents, residues from solvent purification of crude anthracene with phenanthrene solvents, residues from the vaporization of impure anthracene, residues from the vaporization of crude naphthalene, with sulfuric acid and an aldehyde.

ALPHONS O. JAE-GER. HEINRICH W. WITZEL. 

